We have been studying the specific biochemical mechanisms involved in the replication of the autonous parvovirus KRV in a rat nephroma cell line. We have studied transcription of the single-stranded KRV DNA genome both in vivo and in vitro in isolated nuclei. The major viral specific RNA synthesized in both studies is 19 to 22 S and represents a transcript of 60 to 75% of the viral genome. The 5' terminus of the RNA is probably initiated and capped in vitro by the sequence m7G(5') ppp (5')A. We have mapped the RNA using Southern blotting and R-loop technique and find that the KRV mRNA maps from 0.38 to 0.98 on the viral DNA strand. Viral specific RNA transcripts are also found the full length of the viral genome. We hope to determine if post-transcriptional processing occurs and the mechanisms involved. We also plan to use the purified viral mRNA in a cell free protein synthesized system.